Wash and wipe the fruit. Cut in half and squeeze out the juice and pips. Cut the peel into thick shreds and put into a pan with the pulp, juice and water. Tie the pips into a piece of muslin and put into the pan. Boil gently for about two hours, until the mixture is reduced by half. Take out the bag of pips and squeeze it well so that the liquid goes back into the pan. Add the sugar and stir until dissolved. Simmer for one and a half hours until the marmalade is dark and has reached setting point. Leave to stand for fifteen minutes, stir, and put into warm jars. Cover with lids.